Can't use css variables within rgb() and rgba()

[finnhvman]

node-sass throws an error on valid CSS when using var() in rgb() or rgba(), most probably an issue in libsass

Issue in node-sass

input.scss

.test {
  --my-var: 255, 0, 0;
  color: rgb(var(--my-var));
}

Actual results

node-sass 4.11.0 libsass 3.5.4

{ Error: Function rgb is missing argument $green.
    at options.error (/Users/bszabo/WS/sass-test/node_modules/node-sass/lib/index.js:291:26)
  status: 1,
  file: '/Users/bszabo/WS/sass-test/test.scss',
  line: 3,
  column: 10,
  message: 'Function rgb is missing argument $green.',
  formatted: 'Error: Function rgb is missing argument $green.
        on line 3 of test.scss
>>   color: rgb(var(--my-var));
   ---------^
' }

Expected result

dart-sass 1.17.4

.test {
  --my-var: 255, 0, 0;
  color: rgb(var(--my-var));
}

version info:

$ node-sass --version
node-sass       4.11.0  (Wrapper)       [JavaScript]
libsass         3.5.4   (Sass Compiler) [C/C++]

[nschonni]

Duplicate of #2561

[finnhvman]

My bad about the duplicate.

Which libsass release fixes this?

Because it's seemingly still an issue in libsass 3.5.4